Combined metal cover and anti-crush hole support

ABSTRACT

A housings for electronic devices is constructed from a plastic half and a metallic half and provided with a substantially crush-proof mounting foot. The mounting foot is made crush proof/crush resistant by a metallic insert into a plastic outer cylinder or collar. The metallic half and metallic insert are formed at the same time by stamping. The metallic insert is inserted as part of the housing assembly process and does not require a separate manual insertion.

BACKGROUND

Packaging for electronic products continues to move away from heavy andbulky metal enclosures for cost and weight-saving purposes. Whileplastic housings reduce cost and weight, plastic housings can bedifficult to mount because plastics that are usable as housings arebrittle and have relatively low elastic moduli. Mounting flanges or feetare easily crushed when the plastics they are made from are subjected toc compressive stress. Plastics are therefore somewhat ill-suited for useas housings or enclosures of electronic devices.

FIG. 1 is a perspective view of a prior art housing 100 for electronicdevices. The housing 100 is comprised of a plastic top portion 102 and ametallic lower portion 104. Two mounting feet 106 are cantilevered,i.e., they project outwardly, from a side surface 107 of the housing100. The mounting feet 106 are structures that enable the housing 100 tobe attached to a surface.

Each mounting foot 106 is comprised of a plastic upper, generallycylindrically-shaped lug 108. The lug 108 has a hole or cylinder, whichreceives a separately-made and separately installed metallic insertsupport 112. The plastic lug 108 is attached to a second lug 110 that ismetallic and which extends' laterally away from the side 109 of ametallic lower portion 104 of the housing 100. The metal insert 112extends from the top of the plastic lug 108 to the bottom of the secondmetal lug 110.

The metal insert 112 is installed into the foot 106 to provide astructure that can withstand compressive loads applied to the foot 106by fasteners, which are not shown. Fasteners extend through the insert112 and through an attachment surface to which the housing 100 ismounted. The insert 112 thus prevents the plastic lug 108 from beingcrushed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art housing with mounting feethaving separately inserted metal supports;

FIG. 2 is an exploded view of a combined metal cover and anti-crush holeinside a mounting foot;

FIG. 3A is bottom view of the structure depicted in FIG. 2 afterassembly;

FIG. 3B is a top view of the structure shown in FIG. 2 after assembly;

FIG. 4 is an exploded view of a combined metal cover and anti-crush holeformed as part of a mounting foot;

FIG. 5 is cross sectional view of the structure shown in FIG. 4 afterassembly;

FIG. 6 is a top view of an alternate embodiment of a metal cover andanti-crush hole, with the anti-crush hole located interior to a housing;

FIG. 7 and FIG. 8 are assembled and pre-assembled views of an alternateembodiment of a crush-resistant metal portion of a mounting foot;

DETAILED DESCRIPTION

Prior art metal inserts 112 that are inserted separately require manualinsertion. They are also relatively expensive to manufacture becausethey are typically formed by rolling a flat metal tab into a cylinder asshown. Reference numeral 114 identifies a seam formed by rolling theinsert 112. A housing having a combined metal cover and acrush-resistant or an anti-crush hole would be an improvement animprovement over the prior art.

It is well known that the degree to which structures deform in responseto an applied stress depends on the material's modulus of elasticity.When stress and strain are proportional to each other, deformation of amaterial is considered to be elastic. When a material is stressed to itsproportional limit, deformation is plastic, i.e., the material does notreturn to its original shape. Stated another way, a material fails, whenit is subjected to a stress that exceeds its proportional limit or yieldstrength.

Plastics are generally less dense than metals. Plastics are alsogenerally non-conductive. Another difference between plastics and metalsis their elastic modulus. Plastics are not as strong as metals.

Plastics that include low density polyethylene or LDPE, high densitypolyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC)have a modulus of elasticity of about 0.025×10⁶ psi and about 5.0×10⁶psi. Light weight aluminum alloys however have elastic moduli of about10×10⁶ psi. Metals are therefore better able to withstand compressiveloads.

FIG. 2 is an exploded view of a housing 200 comprised of a plastic topportion 202 and a metallic bottom portion 204. The plastic can beamorphous or polycrystalline. The housing 200 has crush-resistant or“anti-crush” supports 206 that extend from exterior sides of the housing200.

The supports 206 are hereinafter referred to as mounting feet. Amounting foot is formed by the joinder or assembly of a top plasticportion 208 of the housing 200 and a metal bottom portion 210 of thehousing 200. The metallic bottom portion 210 is formed to provide ametal, load-bearing insert, which when inserted into a plastic sleeve orcylinder resists crushing when a compressive stress is applied to thefoot 206.

When viewed from the top, the foot 206 has a form reminiscent of astilted arch. As used herein, “stilted arch” refers to an arch having asemi-circular rounded portion with straight legs or stilts that extendaway from the ends of the semi-circular portion. In FIG. 2, the plastictop portion 208 of the mounting foot 206 has an arch-shaped portionidentified by reference numeral 212. Plastic straight legs or stilts 214extend laterally away from a side surface 215 of the plastic top portion202 of the housing 200.

A cylindrical hole 218 is formed in the plastic top portion 208 of thefoot 206. The circular-cross section hole 218 formed into the end of thefoot 206 imbues the top portion 208 of the foot 206 with a structurethat is cylindrical and formed from the plastic material surrounding thecylindrical hole 218. Reference numeral 220 identifies what isconsidered to be the outer circumference of a “cylinder” of material inthe plastic top portion 208 of the foot 206. The plastic top portion 208is thus considered to have a first cylindrical part 220 of the mountingfoot 206.

The bottom portion 210 of the foot 206 is metallic. It therefore has anelastic modulus much greater than the plastic top portion 202.

The bottom portion 210 is comprised of a relatively thin, stiltedarch-shaped tab portion 216 that extends laterally away from a sidesurface 222 of the metallic bottom portion 204.

The bottom portion 204 including the metal tab 216 is formed bystamping. A cylinder 224 extends upwardly from the tab 216 is alsoformed by a stamping process known as deep drawing. Being formed bystamping, the metal cylinder 224 is seamless. And, unlike prior artinserts that are stamped and rolled and therefore not really circular,the cross sectional shape of the stamped metallic cylinder 224 can bemade into a nearly perfect circle.

In addition to being seamless and having nearly perfect circular crosssections, in one embodiment, the stamped metallic cylinder 224 has anoutside diameter that tapers, or which has a “draft.” The outsidediameter at the top of the cylinder 224 is slightly less than theoutside diameter of the cylinder 224 where it meets the tab 216.Providing a draft to the cylinder 224 facilitates assembly of the twopieces 202 and 204 to each other. In other embodiments, the cylinder 224outside diameter is constant.

The bottom or lower end of the cylinder 224 is surrounded by arelatively flat or planar annulus 225, which meets the plastic“cylinder” 220 portion of the plastic top portion 202. The metalliccylinder 224 has a height that is substantially equal to or slightlygreater than the thickness of the plastic first cylindrical part 220 ofthe plastic top portion 208.

By deep drawing the metal lower portion 204, it is possible to stamp alower metal panel 204 having a metallic second cylinder 224, the outsidediameter of which is just equal to the inside diameter of the hole 218in the plastic upper portion of the foot 206. The metallic secondcylinder 224 also has an inside diameter 226 selected to correspond tothe outside diameter of a fastener used to attach the housing 200 to asurface. Fasteners are not shown in FIG. 2 for clarity. A completehousing 200 with a crush-resistant mounting foot 206 is formed when theplastic top portion 202 is joined with the bottom metallic portion 204.

FIG. 3A is a bottom view of the housing 200 shown in FIG. 2. FIG. 3B isa top view of the housing 200.

Together, FIGS. 2, 3A and 3B show that the metallic cylinder 224 of thebottom portion 204 extends orthogonally from the tab 226 and extendscompletely through the thickness of the plastic top portion 208 of thefoot 206. Unlike prior art metal inserts that are inserted manually andwhich have seams, the metallic cylinder 224 slides into the firstplastic cylindrical part 220. The metallic cylinder 224, which extendsthrough the first cylindrical part 220 and which has an elastic modulusgreater than that of the plastic, significantly limits deformation ofthe first cylindrical portion responsive to a compressive loadcompressed on the foot 206 by a fastener. The metallic cylinder 224 thusprovides the mounting foot 206 with an anti-crush hole.

FIG. 4 is an exploded view of one mounting foot 206 that extends fromsides of upper and lower portions of a housing 200 depicted in FIG. 2.FIG. 4 also shows a fastener, comprised of a bolt 401 and hex nut 403,positioned to fasten the two portions of the housing 200 together.

The thickness 402 of the plastic upper portion 208 of the foot 206 isshown to be substantially equal to the height 404 of the metallic secondcylinder 224. Since the height 404 of the inner cylinder 224 is at leastequal to and preferably slightly greater than the thickness 402 of theupper portion 208, insertion of the inner cylinder 224 into thecylindrical hole 218 provides a metallic structure inside a plasticstructure with the metallic structure bearing load applied to themounting foot 206 by a fastener 406. Tightening the hex nut 403 on thebolt 401 exerts compressive force on the metallic inner cylinder 224 butnot on the plastic outer cylinder. In one embodiment, the thickness 402is slightly less than the height 404 to enable the metallic secondcylinder 224 to engage a compressive load before the plastic.

FIG. 5 is a cross sectional view of the assembled foot 206 depicted inFIG. 4. The bolt 401 and hex nut 403 are shown assembled to each otherand attach the housing 200 to a surface 502, such as a surface of ametal chassis of an automobile or other vehicle. By inserting a metalcylinder into the plastic cylinder, compressive stress on the plasticcylinder is significantly reduced or even eliminated.

FIG. 6 is a top view of an alternate embodiment of a housing 600 formedfrom a plastic top portion and a metal bottom portion. Unlike thesupports 206 described above and which extend outwardly from sidewallsof a housing, an anti-crush support 602 is located within the exteriorside walls 604 the housing 600.

FIG. 7 is an exploded view of the housing 600 depicted in FIG. 6 andshowing the structure of the interior-located support 602. A plasticouter cylinder 704 of the support 602 is formed through the plastic topportion 702 of the housing 600. The plastic outer cylinder 704 has aninside diameter 706 large enough to slide over, i.e., receive, aseamless and metallic inner cylinder 708 formed by stamping, andpreferably deep drawing. The metallic cylinder 708 is stamped as part ofa metallic plate from which a metallic bottom portion 710 of the housing600 is formed. As with the embodiment described above, the metallicinner cylinder 708 can be formed with a slight draft or taper tofacilitate assembly of the housing portions.

The metallic inner cylinder 708 has a central hole 712 large enough toreceive a fastener, such as a bolt 714. When the plastic top portion 702is joined to the metallic bottom portion 710, the metallic innercylinder 708 extends all the way through the plastic outer cylinder 704as described above with regard to the exterior foot 206.

FIG. 8 is a side view of the assembled housing 600 of FIG. 6. A bolt 714is shown inserted into the hole 712 that exists in the metallic innercylinder 708. The bolt 714 also extends through a thin, flat panel 800to which the housing 600 is attached by tightening the hex nut 716 onthe bolt 714.

When the fastener 712 and nut 714 are tightened, compressive stress isapplied to the metallic inner cylinder 706. The plastic outer cylinder704 is thus spared from force that might otherwise permanently deform,i.e., crush, the plastic top portion 702 of the housing 600.

In the embodiments described above and depicted in the figures, thecylinders have circular cross sections. Alternate and equivalentembodiments include “cylinders” that have non-circular cross sections,such as square, triangular and rectangular cross sections.

Those of ordinary skill in the art will recognize that a light-weighthousing can be constructed with robust mounting supports by usingsupports formed from both plastic and metallic components. A metallicinsert inside a plastic outer portion is able to withstand compressiveloads greater than having a plastic portion.

The foregoing description is for purposes of illustration only. The truescope of the disclosure is set forth in the appurtenant claims.

1. A housing having a first and second portions and a support, thesupport formed by joinder of the first and second portions to eachother, the support being comprised of: a first cylindrical part; and asecond cylindrical part, the second cylindrical part extending insidethe first cylindrical part and configured to limit deformation of thefirst cylindrical portion responsive to a compressive load impressed onthe support.
 2. The housing of claim 1, wherein the first portion of thehousing and the first cylindrical part are comprised of a first materialhaving a first modulus of elasticity and wherein the second portion ofthe housing and the second cylindrical part are formed from a secondmaterial having a second modulus of elasticity greater than the firstmodulus of elasticity.
 3. The housing of claim 2, wherein the firstmaterial is comprised of a plastic and the second material is metallic.4. The housing of claim 1, wherein the first cylindrical part iscantilevered from a surface of the first housing portion and wherein thesecond support is cantilevered from a surface of the second housingportion.
 5. The housing of claim 1, wherein the second cylindrical partis seamless.
 6. The housing of claim 1, wherein the second cylindricalportion is formed by stamping.
 7. The housing of claim 1, wherein thesecond cylindrical part is tapered.
 8. The housing of claim 1, whereinthe second cylindrical portion has a substantially perfect circularcross section.
 9. The housing of claim 1, wherein the first outercylinder has a first length and a first inside diameter and wherein thesecond cylinder has second length at least as long as the first lengthand an outside diameter less than the first inside diameter, wherebycompressive load on the support is applied to and supported by thesecond cylinder prior to deformation of the first cylinder.
 10. Thehousing of claim 9, wherein the second cylinder is additionallycomprised of an annular foundation, proximate one end of the secondcylinder, extending around the outside of the second cylinder andsupporting the first cylinder.
 11. The housing of claim 1, wherein thesecond cylinder is configured to align the first and second sections ofthe housing to each other.
 12. The housing of claim 1, further comprisedof a fastener extending through the support and applying a compressiveload thereto.
 13. The housing of claim 1, wherein the first portion is atop part of a housing and wherein the second portion is a bottom part ofthe housing.
 14. The housing of claim 1, wherein the second portion issubstantially planar.
 15. A housing comprised of: top and bottomportions and a crush-resistant support, the crush-resistant supportbeing formed by the insertion of a second cylindrical part, formed aspart of the bottom portion, into the interior of a first cylindricalpart that is formed as part of the top portion, the first and secondcylindrical parts being cantilevered from side surfaces of the top andbottom portions respectively, the second cylindrical portion extendingorthogonally from a tab that extends away from the side surface of thebottom portion, the second cylindrical part having an inside diameterselected to receive a fastener to attach the housing, the first andsecond cylindrical parts being configured to align the top and bottomhousing portions to each other when the second cylindrical part isinserted into the first cylindrical part.
 16. The housing of claim 15,wherein the second cylindrical part is a material having a modulus ofelasticity selected to prevent the first cylindrical part from beingdeformed upon the application of a compressive load to the support. 17.The housing of claim 15, wherein the compressive load is applied by thefastener.
 18. The housing of claim 16, wherein the top portion is aplastic and wherein the bottom portion is metallic.
 19. The housing ofclaim 15, wherein the second cylindrical part is tapered and seamless.20. The housing of claim 19, wherein the bottom portion is formed bystamping.